Field of the Invention
The present invention generally relates to a nanoparticulate filler (or nanofiller) of a metal-oxide such as silica, and its usage in a fluorocarbon resin-based aqueous dispersion. The present invention also relates to a non-stick coating comprising such a filler, as well as to a culinary article provided with such a coating.
The synthesis of the nanofiller and the manner in which to achieve the non-stick coating and culinary article are also concerned.
Description of Related Art
The main purpose of the present invention is to introduce as delicately as possible a filler in the form of metal-oxide nanoparticles such as silica in fluorocarbon resin-based non-stick coatings, such as for example polytetrafluoroethylene, (PTFE). For this, it is essential to make the filler (particularly the silica) compatible with the fluorocarbon resin particularly when is in the form an of emulsion comprising a continual aqueous phase and a discontinuous phase constituted by the resin. In fact, the fluorocarbon resin-based non-stick coatings are initially prepared from such emulsions, then are applied onto a substrate and fritted.
A solution known by the skilled person consists in improving the compatibility of the silica nanoparticles with the PTFE by grafting to it a fluorinated chain, such as for example a poly(HEPO)silane which makes the nanoparticles compatible with the PTFE.
However, the major drawback of a silica modified by a poly(HEPO)silane is that it is too hydrophobic and cannot be used in the dispersion formulations of PTFE typically used to achieve non-stick coatings or textile impregnation products. In fact, it is not possible to disperse such a silica in an aqueous medium, and hence much less so in a PTFE emulsion.
The technical issue sought to be resolved by the present invention hence consists more particularly in making the silica (or any other metal oxide usable as a filler in an aqueous dispersion of fluorocarbon resin) compatible with the PTFE (hence hydrophobic), but also dispersible in aqueous medium.